Machines to separate differently sized particles, such as aggregate shakers, sifters, or vibrating screeners are well known in the art, particularly for construction, industrial, and other related applications. These machines include vibrating decks which receive wire screens for separating larger sized particles from smaller sized particles, by shaking loads of aggregate, rocks, dirt, and related material through one or more screens. The screens may have openings arranged to sort particle sizes from a fraction of an inch to several inches, as needed. A single shaker may include a plurality of generally vertically stacked screens for simultaneously separating multiple sizes from the same load of material. Due to the harsh conditions under which the screens are used, the screens have to be replaced regularly. Traditional screens generally comprise two sets of round wires woven perpendicularly together.
To increase the lifespan and decrease the required maintenance of wire screens, self-cleaning screens are also now commonly used. The self-cleaning screens generally include wires which extend in a single longitudinal direction, with a support means to hold the wires in alignment. Thus, each wire can vibrate at its own frequency and the wires can separate from each other, so that rocks or debris will be shaken loose from the screen and the screen will not easily peg or blind. That is, due to the individually vibrating wires, self-cleaning screens do not experience the same level of pegging or blinding as do traditional woven screens.
The support means for some self-cleaning screens comprise small groups of perpendicularly woven wires, which act to support the screen at intervals along the screen. However, the metal-on-metal contact caused by the woven wires increases wear on the screen at the woven sections and decreases the lifespan of the screens. To increase the flexibility and lifespan of the screens, other self-cleaning screens may include a strip of a polymer material formed about and around the groups of perpendicularly woven wires. The polymer support strips are generally made by placing two pre-formed polymer bars or strips, one above the wires and one below, and then welding them together by heating the bars. Although this fuses the two bars together, support members made in this way still suffer from delamination or general weakness at the interface where the two bars are welded together. Even when polymer support strips are used, the perpendicularly woven wires are often required to first also be included, so that the woven wires hold the longitudinal wires of the screen in the final configuration while the polymer strips are formed. Screens which include both a polymer strip and perpendicularly woven wires require additional time, material, and cost to manufacture than traditional screens and inherently have greater variation in spacings between the wires due to gaps between the warp wires that are required for pre-weaving to receive the weft wires. Without the pre-weaving, some other means would be required to at least temporarily hold the wires in the screen's final configuration.
As a result, self-cleaning screens are desired that include the benefits of polymer support members, but not the shortcomings of woven perpendicular wires, and which take less time, material, and cost to manufacture than screens which include both woven wires and polymer support strips. Accordingly, self-cleaning wires would have desired spacings to prevent those problems. Thus, what is, needed a method an apparatus for creating a self-cleaning screen which includes polymer support means and which does not require pre-weaving of other wires, and does not require pre-formed polymer bars or strips.
Conventional wire screens have an obvious trade off wherein increasing opening area requires decreasing diameter of wire and therefore decreases the screen's life. For example, round wires are unable to achieve significant (a) additional through put by providing additional open area and (b) increase of the screen's life. Specifically, increasing the open area of a screen has previously resulted in additional through put that is approximately equal to the increase in the open area. For example, if the open area is increased by 3% then the additional through put previously achieved would be approximately 3%. This is undesirable as the efficiency of conventional screens is limited in that the percentage of additional through put is limited to approximately the same decrease in screen life by approximately the same amount.
Further, previously known screens with wires having a cross-sectional height greater than the cross-sectional width have experienced some upward movement because the the wires were not able to vibrate enough to eliminate or dramatically reduce upward movement of particles. This is undesirable as it can significantly reduce the efficiency of the woven wire screen.
To solve that problem, Hoyt Wire Cloth manufactures a Serpa XLT vibratory screen that abides to the teachings in U.S. Pat. No. 7,581,569. That screen has a woven wire cloth extending in a substantially flat plane. The woven wire cloth has a plurality of warp wires and a plurality of weft wires. Each of the warp wires and each of the weft wires have a cross-sectional height extending substantially perpendicular to the plane of the woven wire cloth and a cross-sectional width extending substantially parallel to the plane of the woven wire cloth. The warp wires are arranged substantially parallel to each other, disposed completely in a common horizontal plane limited by a dimension of the cross-sectional height of the warp wire, and defining openings in the woven wire cloth for the passage of material there through. The weft wires extend substantially perpendicular to the warp wires, the weft wires being woven through the warp wires in groups at spaced intervals. The Serpa XLT screen utilizes round wire that is compressed and formed into an “oblong” configuration design. These crimped “oblong” wires are then woven to create the Serpa XLT screen.
The prior art weaves the weft and warp wires together first and then, optionally, overcoats the wires to protect the weft wires. The overcoat is not used to set the position of the warp wires, instead the overcoat layer is used to protect the weft wires. Moreover, the warp wires are merely overcoated by a polymeric material. Those significant facts are confirmed in U.S. Pat. No. 7,581,569 wherein it was expressed, “the weft wires . . . are disposed substantially in a common plane and are arranged substantially parallel to each other. The weft wires . . . extend substantially perpendicular to the warp wires . . . . The weft wires . . . are woven through the warp wires . . . in groups . . . that are arranged at spaced intervals. The number of the groups . . . of the weft wires . . . and the number of weft wires . . . in each of the groups . . . may vary depending on dimensions and desired configuration of the woven wire cloth . . . . The weft wires . . . may be woven through the warp wires . . . , for example, by a double or triple heddle loom. The weft wires . . . maintain the warp wires . . . in spaced relation to each other. Alternatively or in addition to the weft wires . . . , the warp wires . . . may be maintained in spaced relation to each other by molding the warp wires . . . together at spaced intervals. The warp wires . . . may be molded together, for example, with a polyurethane or rubber material.” (see col. 3, lines 1 to 16) and as illustrated at Hoyt's Serpa XLT™ Screens brochure (which is being provided in an information disclosure statement) wherein the orange polymeric material, illustrated at the bottom of the first page, overcoats the the warp wires where the weft wires exist. Overcoating warp wires, without weft wires, is impractical for Hoyt's Serpa XLT™ Screens because the warp wires will not retain their spaced relationship to each other without the weft wires; in addition Hoyt only manufactures screens with both warp and weft wires, and sometimes with a polymeric overcoat over the warp wires where the weft wires are positioned. Based on Hoyt's vague teaching in the '569 patent—fails to disclose any polymeric material in the figures and baldly asserts an alternative embodiment without any disclosing how to implement it—and how Hoyt actually applies the polymeric material in its Serpa XLT™ Screens, one understands and appreciates that weft and warp wires are required in screens with an optional polymeric overcoat layer to inhibit pitting from occurring at the junction of the weft and warp wires.
In the formation of the Serpa XLT Screens, the warp wires, prior to being overcoated have gaps (which Hoyt identifies as spacing intervals) between each warp wire to accommodate the weaving procedure that occurs with the weft wire. Those gaps allow the warp wires to migrate away (see box 88) and toward (see box 89) respective adjacent warp wires which results in wide and narrow opening sizes as illustrated in FIG. 14. The resulting variations or deviations from the screen spacing illustrated in FIG. 14 are greater than the standard industry tolerance as established by ASTM E2016-11, table 8 and those aperture deficiencies were caused by the movement of the warp wires, which the instant invention avoids and/or significantly decreases.
Another problem with the Serpa XLT Screens is that the overcoat urethane material positioned exclusively over the warp and weft wires where the weft wires exist deteriorates at an accelerated rate when used in production facilities. A potential reason for the accelerated deterioration is because the urethane coating is too thin, and without the weft wires the coating could be thicker which may solve this specific Serpa problem.
In addition, the use of weft wires significantly decreases the warp wires' vibration. The decreased vibration stiffens and therefore strengthens the warp wires' sheer wall effect. The sheer wall effect occurs when two wires have a pegged object clogged between the two wires and the pegged object is difficult to unclog or cleaned from the screen. The sheer wall effect is noticeable with the oblong wires due to the oblong wires have “parallel” walls that extend the height of the wires. That sheer wall effect is not noticeable with round wires, which is not a subject of the claimed invention, since the alleged sheer wall effect with round wires is essentially a point on each wire that is closest to an adjacent point on another wire.
The sheer wall effect was not an issue in commonly assigned U.S. Pat. No. 8,353,407 since round wires were utilized. In particular, its support member(s) could be located anywhere on the round wires since the vibration effect was not relevant since there was a minimal sheer wall effect. It was only after applicant applied flattened wire did applicant realize that the location between support members on each screen and the width of each support member was critical in obtaining the desired vibration effect to overcome the sheer wall effect.
The current embodiment of the present invention solves the above-identified problems.